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HISTORY Although the Band Theory of solids had been very successful in describing various electrical properties of materials, in 1937 J H de Boer and E J W Verwey pointed out that a variety of transition metal oxides that were predicted to be conductors by band theory were in fact insulators[1]. Nevill Mott and R. Peierls then predicted that this anomaly could be explained by including interactions between electrons[2]. In 1949, in particular, Mott proposed a model for NiO as an insulator, in which conduction could be understood by the formula {Link without Title} : :(Ni2+O2-)2 --> Ni3+O2- + Ni1+O2- In this situation, the formation of an energy gap preventing conduction can be understood as the competition between the Coulomb potential U between 3d electrons, and the transfer integral t of 3d electrons between neighbouring atoms (the transfer integral is a part of the tight-binding approximation). The total energy gap is then: :Egap = U - 2zt where z is the number of nearest neighbour atoms. In general, Mott insulators occur when the repulsive Coulomb potential U is large enough to create an energy gap. One of the simplest theories of Mott insulators is the Hubbard Model . APPLICATIONS Mott insulators are of growing interest in advanced Physics research, and are not yet fully understood. They have applications in thin-film magnetic heterostructures and high-temperature superconductivity. SEE ALSO REFERENCES {Link without Title} J H de Boer and E J W Verwey, Proceedings of the Physical Society of London 49, 59 (1937). {Link without Title} N F Mott and R Peierls, Proceedings of the Physical Society of London 49, 72 (1937). {Link without Title} N F Mott, Proceedings of the Physical Society of London Series A 62, 416 (1949). |
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